The head of the Canadian railway company whose train derailed and crashed into a small Quebec town has been taken in for police questioning after saying that an employee failed to set the train's brakes properly.

Edward Burkhardt, the chairman of the Montreal, Maine, & Atlantic Railways, was led away by police after holding a news conference in Lac-Megantic, the town that was set ablaze when the runaway train barrelled into it early Sunday morning.

Fifteen people died in the crash and ensuing fire, and another 45 people are still missing.

Burkhardt said at the conference that he believes the train's engineer did not set the hand brakes before leaving the train for the night, despite the engineer saying otherwise.

"It was questionable whether hand brakes were put in place at this time," Burkhardt said. "I don't think any employees removed brakes. They failed to set the brakes."'

He said a train engineer had been suspended without pay.

Authorities in Canada have not yet determined what caused the train to come loose from its parking place at the rail yard at Nantes, Quebec, just uphill from the town of Lac-Megantic.

Canada's Transportation Safety Board manager Rob Johnston told ABC News Tuesday that authorities were investigating whether there were operational errors, including a lack of brakes, that could have led to the runaway train.

Johnston said that investigators were also focusing on how a small fire that broke out in the train's locomotive late Saturday night, and was extinguished before midnight, may have played a role in the train breaking free early Sunday morning.

The 73-car freight train was carrying up to 1 million gallons of petroleum crude oil when it began rolling away from Nantes around 12:50 a.m. The train then derailed and the cars became detached from the locomotive, causing the train and oil to explode into a ball of fire.

"The unmanned trains started to descend down a rolling grade to the center of Lac-Megantic," TSB manager Rob Johnston said Tuesday. "In this area there are no types of track circuits, so the rail traffic controller would have had no way to know the train had moved."

As the train crashed into Lac-Megantic, the fire spread, destroying at least 30 homes in the town and forcing about 2,000 residents to evacuate.

Many of the missing are believed to have been at a bar, Le Musi-Cafe, at the time of the accident. The train is believed to have struck the bar while on fire.

"This was an incredible accident," Johnston said. "All of our people want to do everything we can to do get to the bottom of this and make sure it doesn't happen again. "